Add "error" method to the Result interface in Pigeon

Use case

I'm using Pigeon to generate type-safe interop with native platforms.
In the case of @async functions, it generates the following interface in Java

public interface Result<T> {
    void success(T var1);
}

It has no way to report an error.

My use case is to call some method on the Host, and in case of any error, I need to show an error popup on the Flutter side.

Proposal

I suggest adding error method to the interface

    public interface Result<T> {
        void success(T var1);
        void error();
    }

@gaaclarke

/cc @gaaclarke

Yea, here is the caller of the callback:

      {
        BasicMessageChannel<Object> channel =
            new BasicMessageChannel<>(binaryMessenger, "dev.flutter.pigeon.Api2Host.calculate", new StandardMessageCodec());
        if (api != null) {
          channel.setMessageHandler((message, reply) -> {
            Map<String, Object> wrapped = new HashMap<>();
            try {
              @SuppressWarnings("ConstantConditions")
              Value input = Value.fromMap((Map<String, Object>)message);
              api.calculate(input, result -> { wrapped.put("result", result.toMap()); reply.reply(wrapped); });
            }
            catch (Error | RuntimeException exception) {
              wrapped.put("error", wrapError(exception));
              reply.reply(wrapped);
            }
          });
        } else {
          channel.setMessageHandler(null);
        }
      }

We should have a way to fill in wrapped.put("error", wrapError(exception)) in response to the callback.

As a workaround for now you can include an error in your pigeon class:

class QueryResult {
  String? error;
  String? result;
}

@HostApi()
abstract class Api {
  @async QueryResult query();
}

+1.

We just ran into needing this as well. Would be nice to have.

+1

yes, I think this is needed.

Trying to have an object that represents an error doesn't work for me:

class ErrorClass {
     final int code;
     final String message;
     
     ErrorClass({required this.code, required this.message});
}

class ResultType {
    final string someValue;
    
    ResultType({required this.someValue});
}

class Reply {
       final ErrorClass? error;
       final ResultType? result;
       
       Reply({this.error, this.result});
}

and returning something like error = null and result != null or vice versa from Java / Kotlin, throws a null reference exception stating that error is null but it should not be null when calling error.toMap() for example.

Attempt to invoke virtual method 'java.util.Map x.y.z.ErrorClass.toMap()' on a null object reference

any news?

Fixed in flutter/packages#460, It took a while because I didn't want to implement it until the testing framework for the java generator was improved.

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

Navigation Menu

Repository navigation

Add "error" method to the Result interface in Pigeon #83244

Use case

Proposal

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Add "error" method to the Result interface in Pigeon #83244

Description

Use case

Proposal

Activity

stuartmorgan-g commented on May 27, 2021

gaaclarke commented on May 28, 2021

ajmalk commented on Jul 17, 2021

AhmedNourJamalElDin commented on Jul 17, 2021

cenumi commented on Sep 6, 2021

gaaclarke commented on Sep 7, 2021

github-actions commented on Sep 22, 2021

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions